Safe T Sorb would be way more affordable than Flourite. Have you considered it? $4 for 40 pounds, usually. Or just under $10 for 40 pounds shipped directly to your doorstep from Drillspot/Grainger.
The tank is small enough that it wouldn't be unrealistic to use ADA Aquasoil, though. Depending upon budget.
Reefing isn't really difficult. At least not more difficult than the stuff we do on TPT. But coral is expensive as all get out, skimmers are expensive, the lighting you need will cost you easily $300-$400. The initial salt investment is expensive. You'd want an auto top-off system.
Have you thought about maybe scaping a chamber of your giant sump and leaving it open for viewing? Wouldn't have to cover the front of the stand if you went that route. If there were chambers you didn't want to be visible, it would be cheap and easy to cover the front of them with black vinyl or removable black acrylic/plastic sheets.